Arylidene semicarbazones and their utility as herbicides

ABSTRACT

Substituted-arylidene semicarbazone having the formula:   IN WHICH Z represents oxygen, X represents halogen, lower alkoxy, lower alkyl, hydroxyl, nitro, cyano, N-allylcarbamoyloxy, lower-dialkylthiophos-phoryloxy, N-lower alkylcarbamoyloxy, lower dialkylamino, or (CH3)3N I ; n represents an integer of from 0 to 3, inclusive; R represents hydrogen or lower alkyl; R1 represents hydrogen or lower alkyl; R2 represents, lower alkyl or allyl; R3 represents hydrogen, alkyl, allyl, furfuryl, tetrahydrofurfuryl, lower alkoxy lower alkyl, cyclohexyl, 2-chloroallyl, phenyl, benzyl, or substituted-phenyl in which the substituents are chloro or nitro; R2 and R3 when taken together represent an alkylene containing four to six carbon atoms, inclusive or lower alkyl substituted alkylene containing five to eight carbon atoms, inclusive. The compounds are useful as herbicides.

[4 Aug. 21, 1973 ARYLIDENE SEMICARBAZONES AND THEIR UTILITY AS IIERBICIDES [75] Inventor: Harry Tllles, El Cerrito, Calif.

[73] Assignee: Staufier Chemical Company,

Westport, Conn.

[22] Filed: May 14, 1970 [21] App]. No.: 48,733

Related [1.8. Application Data [62] Division of Ser. No. 773,657, Nov. 5, 1968,

abandoned.

[52] US. Cl. 71/120, 71/70, 71/71, 7l/72, 71/74, 71/76, 71/77, 71/87, 71/88,

[51] Int. Cl A0ln 9/20 [58] Field of Search 71/121, 120, 118,

[56] References Cited UNITED STATES PATENTS 3,031,292 4/1962 Todd 71/120 3,125,601 3/1964 Goebel 71/120 3,591,636 7/1971 Houlihan et al. 71/121 3,382,061 5/1968 Bondarenko et al. 71/120 3,194,835 7/1965 Muller 71/98 3,182,082 5/1965 Sydor 260/552 3,419,659 12/1968 Catino et a1 424/60 2,412,510 12/1946 Jones 71/98 OTHER PUBLICATIONS Dufrenoy Mycobacteriostatic Agents and Chemicals Controlling etc, (1953).

Pratt et al. Growth Reg. Props. of Some Thisemicar: bazones etc." (1952).

Primary Examiner-Lewis Gotts Assistant Examiner-Ci. Hollrah Atrorney-Wayne C. Jaeschke and. Edwin H. Baker ABSTRACT Substituted-arylidene semicarbazone having the formula:

in which Z represents oxygen, X represents halogen, lower alkoxy, lower alkyl, hydroxyl, nitro, cyano, N- allylcarbamoyloxy, lower-dialkylthiophos-phoryloxy, N-lower alkylcarbamoyloxy, lower dialkylamino, or (CI-I N*I; n represents an integer of from 0 to 3, inclusive; R represents hydrogen or lower alkyl; R represents hydrogen or lower alkyl; R represents, lower alkyl or allyl; R represents hydrogen, alkyl, allyl, furfuryl, tetrahydrofurfuryl lower alkoxy lower alkyl, cyclohexyl, 2-chloroa1lyl, phenyl, benzyl, or substituted-phenyl in which the substituents are chloro or nitro; R and R when taken together represent an alkylene containing four to six carbon atoms, inclusive or lower alkyl substituted alkylene containing five to eight carbon atoms, inclusive. The compounds are useful as herbicides.

34 Claims, No Drawings ARYLIDENE SEMICARBAZONES AND THEIR UTILITY AS HERBICIDES This application is a division of copending US. Pat. application Ser. No. 773,657 filed Nov. 5, 1968 now abandoned.

This invention relates to certain novel substitutedarylidene semicarbazone compounds which are useful as herbicides. The compounds of the present invention are new compositions of matter and correspond to the formula:

in which Z is oxygen; X is halogen, lower alkoxy, lower alkyl, hydroxyl, nitro, cyano, N-lower alkylcarbamoyloxy, N-allylcarbamoyloxy, lower dialkylamino, lower dialkylthio-phosphoryloxy or (CH ):,N I; n is an integer of from to 3, inclusive; R is hydrogen or lower alkyl; R is hydrogen or lower alkyl; R is hydrogen, lower alkyl or allyl; R is lower alkyl, allyl, furfuryl, tetrahydrofurfuryl, lower alkoxy lower alkyl, cyclohexyl, 2-chloroallyl, phenyl, benzyl or substituted-phenyl in which said substituents are chloro or nitro; R and R when taken together is alkylene containing four to six carbon atoms, inclusive, or lower alkyl-substituted alkylene containing a total of five to eight carbonatoms, inclusive.

In the above description, the following preferred embodiments are intended for the various groups: lower alkyl preferably includes, unless otherwise provided for, those members which contain from one to about six carbon atoms, inclusive, in both straight chain and branched chain configurations, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec.-butyl, amyl, isoamyl, n-hexyl, isohexyl, and the like; lower alkoxy preferably includes those members which contain from one to about four carbon atoms, inclusive, in both straight chain and branched chain configurations, for example, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec. -butoxy and isobutoxy; the term halogen preferably includes fluorine, chlorine,bromine and iodine. When the term lower alkyl appears as a substituent in a group, such as lower alkyl carbamoyloxy and lower dialkylamino, the term preferably includes those lower alkyl members which contain from one to about four carbon atoms, inclusive, in both straight chain and branched chain configurations; and lower alkoxy lower alkyl preferably includes those members which contain a total of not more than six carbon atoms, for example, methoxymethyl, methoxyethyl, ethoxymethyl, methoxypropyl, ethoxypropyl, propoxypropyl, ethoxybutyl, methoxyamyl, and the like.

The compounds of this invention have been found to be active herbicides of a general type. That is, certain members of the class have been found to be herbicidally effective against a wide range of plant species. The method of controlling undesirable vegetation of the present invention comprises applying an herbicidally effective amount of the above-described compounds to the area where control is desired.

An herbicide is used herein to mean a compound which'controls or modifies the growth of plants. By a growth controlling amount is meant an amount of compound which causes a modifying effect upon the growth of plants. Such modifying effects include all deviations from natural development, for example, killing, retardation, defoliation, desiccation, regulation, stunting, tillering, stimulation, dwarfing and the like. By plants it'is meant germinzant seeds, emerging seedlings, and established vegetation including the roots and above-ground portions.

The compounds of the present invention are prepared by several different methodsdepending upon the nature of the starting materials and the products desired. The following general schemes illustrate the various synthesis routes that can be used for preparing the subject compounds.

A. l-Arylidene-4-mono or disubstituted semicarba- B. l-Arylidene-4-monosubstituted semicarbazones.

C. l-Arylidene-4-mono or disubstituted semicarba- LII - able acid acceptor, such as triethylamine is used as a catalyst. Where water is eliminated, such as in route A) supra, a catalyst, such as 2-naphthalenesulfonic acid, is

EXAMPLE 1 Preparation of 1-Benzylidene-2-Methyl-4-Isopropylsemicarbazone.

A 500 cc four-necked flask is provided with a stirrer,

thermometer, condenser and a Dean-Stark water azeotrope apparatus. A mixture of 10.6 g. (0.10 mole) of .benzaldehyde, 13.1 g. (0.10 mole) of 2-methyl-4- isopropyl-semicarbazone, 0.3 g. of 2-naphthalenesulfonic acid and 100 cc of benzene is charged to the flask. The mixture is heated to reflux with stirring and is refluxed for 2 hours until no more water is azeotroped. The reaction mixture is then cooled to room temperature,'washed with four 50 cc portions of water, dried over anhydrous magnesium sulfate and concentrated on the rotary evaporator under reduced pres- ANALYSIS Calculated for C,,H N,O: C, 65.72 percent; H, 7.81

percent Found: c, 66.01 percent; H, 7.87 percent 40 EXAMPLE 11 Preparation of 1-(p-Methy1benzylidene)-2-Methyl-4- t-butylsem icarbazone.

Para-Tolualdehyde methylhydrazone, 10.4 g. (0.07 mole) is dissolved in 25 cc of anhydrous diethyl ether and 8.3 g. (0.084 mole) of t-butyl isocyanate is added. The reaction mixture is allowed to stand at room temperature for 20 hours and is concentrated under reduced pressure. The residual viscous liquid, 15.9 g., is induced to crystallize by scratching and is recrystallized from hexane and filtered after cooling the mixture in 4 ANALYSIS:

Calculated for C H NSO: C, 67.98 percent; H, 8.56

percent;

Found: C, 67.71 percent; H, 8.29 percent EXAMPLE ll 1 Preparation of 1-(o-Chlorobenzy1idene)-2-Methy1-4- lsobutylsemicarbazone.

A 500 cc four-necked flask is provided with stirrer, thermometer, condenser and addition funnel. To the flask is added 1 1.6 g. (0.05 mole) of chloroformic acid, (o-chlorobenzylidene) methylhydrazide and 100 cc of benzene. A mixture of 4.0 g. (0.055 mole) of isobutylamine and 5.6 g. (0.055 mole) of triethylamine is added dropwise to the flask over an interval of 5 minutes while cooling with ice and the temperature is main- I tained between 22 26 C. The mixture is then brought to reflux and held at reflux for 20 minutes. The mixture is cooled, filtered from triethylamine hydrochloride, the cake washed with four 25 cc portions of benzene and the washings are combined with the original benzene filtrate. The combined benzene filtrate is washed with four 50 cc portions of water, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. There is obtained 1 1.9 g. (88.8 percent yield) of the title compound, m.p. 98.0 100.5 C.

ANALYSIS Calculated for c,,H,,c,N,o= C, 58.31 percent; H, 6.78 percent;

Found: C, 58.48 percent; H, 6.92 percent EXAMPLE 1V Preparation of Ethylcarbamoyloxybenzylidene)-2-Methyl-4-isopropylsemicarbazones.

A 100cc three-necked flask is provided with stirrer, thermometer and condenser containing a drying tube filled with drying agent connected to its top. To the flask is charged 11.8 g. (0.05 mole) of l-(3'- hydroxybenzylidene)-2-methyl-4-isopropylsemicarbazone) 50 cc of anhydrous acetone and 5 drops of triethylamine. To this mixture is charged 5.3 g. of ethyl isocyanate. The mixture is then refluxed for 3 hours, cooled and concentrated under reduced pressure. The residual solid is washed with four 50 cc portions of water and dried. There is obtained 14.8 g. (96.7 percent yield) of the title compound, m.p. 143.0 144.5 C.

ANALYSlS Calculated for C, -,H, N O,: C, 58.80 percent; H, 7.24

dry ice. There is obtained 6.0 g. (34.7 percent yield) of percent; the title compound, m.p. 77 80 C. Found: C, 58.93 percent; H, 7.51 percent TABLE 1 i l i C=NNCN Compound number x. R R1 z R1 R3 M.P. cc. 1m

H CH; 0 H CH; lets-164.5. H CH; 0 H "-0.11, 89:90. H CH; O H t-C4H. 77-80. H CH; 0 H CH; 114-116.

TABLE 1- Continued Compound number Xn R R Z R R M.P. 0.) u

H CaHs O H H (32H; H H (31H; 0 H

H CH 0 CHz =CHCHz H i-C;H1 0 H H CH; O H H CH 0 H H CH3 0 H H i-C H1 O H H i-CgH1 O H H i-C H1 O H CH3 CH: O H CH; CH; O H CH: CH; O H CH3 CH: O H CH; CH; O H CH3 CH; O H CH3 H O H OH; H O H CzHs H O H CH; CH: O H CH CH; 0 H CH CH 0 H H H: S H H CH3 3 H H CH S H H CH; 8 H H CH: 5 H H CH; 8 H

Other examples of compounds falling within the generic formula presented herein, which are preparable by the aforedescribed procedures and which may be formulated into herbicidal compositions and applied as herein illustrated are:

HERBICIDAL SCREENING TESTS As previously mentioned, the herein described compounds produced in the above-described manner are phytotoxic compounds which are useful and valuable in controlling various plant species. Compounds of this invention are tested as herbicides in the following manner.

Pre-emergence Herbicide Test On the day preceding treatment, seeds of seven different weed species are planted in individual rows using one species per row across the width of the flat. The seeds used are hairy crabgrass (Digitaris sanguinalis (L.) Scop.), yellow foxtail (Setaria glauca (L.) Beauv.), watergrass (Echinochloa crusgalli (L.) Beauv.), California red oat (Avena Sativa (L.), redroot pigweed (Amaranthus retroflexus (L.), Indian mustard (Brassica juncea (L.) Coss.) and curly dock (Rumex crispus (L). Ample seeds are planted to give about to 50 seedlings per row, after emergence, depending on the size of the plants. The flats are watered after planting. The spraying solution is prepared by dissolving 50 mg. of the test compound in 3 ml. of a solvent, such as acetone, containing 1 percent Tween 20 (polyoxyethylene sorbitan monolaurate). The following day each flat is sprayed at the rate of 20 pounds of the candidate compound per 80 gallons of solution per acre. An atomizer is used to spray the solution onto the soil surface. The flats are placed in a greenhouse at 80 F. and watered regularly. Two weeks later the degree of weed control is determined by comparing the amount of germination and growth of each weed in the treated flats with weeds in several untreated control flats. The rating system is as follows:

no significant injury (0-15 per cent control) slight injury (25-35 per cent control) -H- moderate injury (55-65 per cent control) l-H- severe injury or death (-100 per cent control) An activity index is used to represent the total activity on all seven weed species. lt is the sum of the number of plus marks, so that an activity index of 21 represents complete control of all'seven weeds. The results of this test are reported in Table ll.

Post-emergence Herbicide Test Seeds of five weed species including hairy crabgrass, watergrass, California red oats, Indian mustard, and curly dock and one crop, pinto beans (Phaseolus vulgaris), are planted in flats as described above for pro-emergence screening. The flats are placed in the greenhouse at 72-85 F. and watered daily with a sprinkler. About 10 to 14 days after planting when the primary leaves of the bean plant: are almost fully expanded and the first trifoliate leaves are just starting to form, the plants are sprayed. The spray is prepared by weighing out 50 mg. of the test compound, dissolving it in 5 ml. of acetone containing 1 percent Tween 20 (polyoxy-ethlene sorbitan monolaurate) and then adding 5 ml. of water. The solution is sprayed on the foliage using an atomizer. The spray concentration is 0.5 percent and the rate would be approximately 20 lb/acre if all of the spray were retained on the plant and the soil, but some spray is lost so it is estimated that the application rate is approximately 12.5 lb/acre.

Beans are used to detect defoliants and plant growth regulators. The beans are trimmed to two or three plants per flat by cutting off the excess weaker plants several days before treatment. The treated plants are placed back in the greenhouse and care is taken to avoid sprinkling the treated foliage with water for three days after treatment. Water is applied to the soil by means of a slow stream from a watering hose taking care not to wet the foliage.

Injury rates are recorded 14 days after treatment. The rating system is the same as described above for the pre-emergence test where (l+), and (+-l+-) are used for the different rates of injury and control. The injury symptoms are also recorded. The maximum activity index for complete control of all the species in the post-emergence screening test is 18 which represents the sum of the plus marks obtained 9609756423 447030630 7967 34775665959855 0 77 3566 l lull-Illil. l .l I. 1

ill

296744460772 4227 til 1 I.

" 21 85-l00% control of all seven plant species tested prel8 85-l00% control of all six plant species tested post-emergence.

The compounds of the present invention are used as pre-emergence or post-emergence herbicides and are applied in a variety of ways at various concentrations. In practice, the compounds are formulated with an inert carrier, utilizing methods well-known to those skilled in the art, thereby making them suitable for application as dusts, sprays, or drenches and the like in the form and manner required. The mixtures can be e c w W 0 234567890 234567890 234567890 234567890 2 4 567890 234567890 234567 e 789 23456789000000 %m llllllwmwmHHHHHHHHHHHHnnnnnnnnnwnwwnwnBBMMMMMMMMMMUHUUUUUUUUMMWMMMMM m 0 5 0 5 0 5 0 5 0 5 0 5 5 l l 2 2 3 3 4 4 5 5 6 6 e e 460376207 266232586238645766642485 5 l d 5 mm 11 111 111 1 11 1 11 1 n w1 n U mm w w m m u 1nn mn 1 m T m. .m .L 5 e r U m2 e S e l h E m u e R h P T o w M m m m N e 5702 46356230972030522023422300000075198078300000440000000000000260204 40200844 0 00 E c l l l l 2 l 1 Ill 1 l .1. 1 e1 mw h E l t r .l. R .m o mm 1 C me E S H w e L Y m m B T P n A I S .t .w n T V I c w T e 0 P C s A t s M.. Lv w A e D .m 1. m m d e y B n h ur til R De h V E Pb t n mm .M c H DU O a 34567890 234567890 2345678902345670090 234567890 2345670090234567890 23456 dispersed in water with the aid of a wetting agent or they can be employed in organic liquid compositions, oil and water, water in oil emulsions, with or without the addition of wetting, dispersing or emulsifying agents. The amount applied depends upon the nature of the seeds or plants to be controlled and the rateof application varies from 1 to approximately 50 pounds per acre. 1 i

The phytotoxic compositions of this invention are applied to the plants in the conventional manner. Thus, the dust and liquid compositions can be applied to the plant by the use of power-dusters, boom and hand sprayers and spray-dusters. The compositions can also be applied from airplanes as a dust or a spray because they are effective in very low dosages. In order to modify or control growth of germinating seeds or emerging seedlings, as a typical example, the dust and liquid compositions are applied to the soil according to conventional methods and are distributed in the soil to a depth of at least ya-inch below the soil surface. It is not necessary that the phytotoxic compositions be admixed with the soil particles and these compositions can be applied merely by spraying or sprinkling the surface of the soil. The phytotoxic compositions of this invention can also be applied by addition to irrigation water supplied to the field to be treated. This method of application permits the penetration of the compositions into the soil as the water is absorbed therein. Dust compositions, granular compositions or liquid formulations applied to the surface of the soil can be distributed below the surface of the soil by conventional means such as discing, dragging or mixing operations.

The phytotoxic compositions of this invention can also contain other additaments for example, fertilizers,

pesticides and the like, used as adjuvant or in combination with any of the above-described adjuvants. Other phytotoxic compounds useful in combination with the above-described compounds include for example, 2,4-dichlorophenoxyacetic acids, 2,4,5-trichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxy-acetic acid and the salts, esters and amides thereof; triazine derivatives, such as 2,4-bis(3-methoxypropylamino)-6- methyl-thio-S-triazine; propylamino-S-triazine, and 2-ethylamino-4- isopropylamino-G-methylmercapto-S-triazine, urea derivatives, such as 3-(3,4-dichlorophenyl)-1,l-dimethyl urea and 3-(p-chlorophenyl)-l ,l-dimethyl urea and acetamides such as N,N-diallyl-a-chloroacetamide, N- (a-chloroacetyl)hexamethylene imine, and N,N-diethyl-a-bromace-tamide, and the like; benzoic acids such as 3-amino-2,S-dichlorobenzoic and; thiocarbamates, such as S-propyl dipropylthiocarbamate; S-ethyl-dipropylthiocarbamate, S-ethyl-cyclohexylethyl-thiocarbamate, S-ethyl hexahydrol ll-azepinel carbothioate and the like. Fertilizers useful in combination with the active ingredients include for example, ammonium nitrate, urea and superphosphate. Other useful additaments include materials in which plant organisms take root and grow such as compost, manure, humus, sand and the like.

, The concentration of a compound of the present invention, constituting an effective amount in the best mode of administration in the utility disclosed is readily determinable by those skilled in the art.

Various changes and modifications are possible without departing from the spirit and scope of the invention described herein and will be apparent to those skilled 2-chloro-4-ethylamino-6-iso-' in the art to whichit pertains. It is accordingly intended that the present invention shall only be limited by the scope of the claims.

What is claimed is:

l. A method for controlling the growth of undesirable vegetation which comprises applying to the area where control of said vegetative growth is desired, an herbicidally effective amount ofa compound having the formula: 0

in which Z is oxygen;

X is chlorine, bromine, lower alkoxy, lower alkyl, hy-

droxyl, nitro, cyano, lower dialkylamino, or a)a n is an integer of from 0 to 3, inclusive;

R is hydrogen or lower alkyl;

R is hydrogen or lower alkyl;

R is hydrogen, lower alkyl or allyl;

R is lower alkyl, allyl, lower alkoxy lower alkyl, cy-

clohexyl, 2-chloroallyl, phenyl, benzyl, or substituterl-phenyl in which saidfsubstituents are chloro or nitro.

2. A method according to claim 1 in which X is lower alkyl, R is hydrogen, R is lower alkyl, R is hydrogen, R is lower alkyl and n is l.

3. A method according to claim 2 in which X is 4- methyl, R is methyl and R is n-butyl.

4. A method according to claim 2 in which X is 4- methyl, R is methyl and R is t-b'utyl.

5. A methodaccording to claim 2 in which X is 4- methyl, R is methyl and R? is methyl.

6. A method according to claim 2 in which X is 4- methyl, R is methyl and R is ethyl.

7. A method according to claim 2 in which X is 4- methyl, R is methyl and R is isopropyl.

8. A method according to claim 2 in which X is 2- methyl, R is methyl and R is isopropyl.

9. A method according to claim 2 in which X is 2- methyl, R is methyl and R is t-butyl.

10. A method according to claim 1 in which n is 0, R is hydrogen, R is lower alkyl, R is hydrogen and R is lower alkyl.

11. A method according to claim 10 in which R is methyl and R is t-butyl.

12. A method according to claim 10 in which R is methyl and R is t-butyl.

13. A method according to claim 1 in which X is chlorine, R is hydrogen, R is lower alkyl, R is hydrogen, R is lower alkyl and n is l.

14. A method according to claim 13 in which the chlorine is in the 4-position, R is. methyl and R is methyl.

15. A method according to claim 13 in which the chlorine is in the 4-position, R is methyl and R is tbutyl.

16. A method according to claim. 13 in which the chlorine is in the 2-position, R is. methyl and R is tbutyl.

17. A method according to claim. 13 in which the chlorine is in the 4-position, R is methyl and R is isopropyl.

18. A method accordingto claim 13 in which the chlorine isin the 2-position, R is methyl and R is isopropyl.

19. A method according to claim 13 in which the chlorine is in the 3-position, R is methyl and R is tbutyl.

20. A method according to claim 13 in which the chlorine is in the 3-position, R is methyl and R is isopropyl.

21. A method according to claim 13 in which the chlorine is in the 2-position, R is methyl and R is ethyl. a

22. A method according to claim 13 in which the chlorine is in the 2-position, R is methyl and R is methyl.

23. A method according to claim 13 in which the chlorine is in the 2-position, R is methyl and R is npropyl.

24. A method according to claim 13 in which the chlorine is in the 2-position, R is methyl and R is nbutyl.

25. A method according to claim 13 in which the chlorine is in the 2-position, R is n-butyl and R is isopropyl.

26. A method according to claim 13 in which the chlorine is in the 2-position, R is n-butyl and R is tbutyl.

27. A method according to claim 13 in which the chlorine is in the 2-position, R is n-butyl and R is methyl.

28. A method according to claim 1 in which X is lower alkoxy, R is hydrogen, R is lower alkyl, R is hydrogen, R is lower alkyl and n is l.

29. A method according to claim 2 in which X is 4- methoxy, R is methyl and R is t-butyl.

30. A method according to claim 28 in which X is 4- methoxy, R is methyl, and R is isopropyl.

31. A method according to claim 28 in which X is 2- methoxy, R is methyl and R is t-butyl.

32. A method according to claim 1 in which X is lower alkoxy, R is hydrogen, R is lower alkyl, R is hydrogen, R is lower alkyl and n is 2.

33. A method according to claim 32 in which X is 3,4-dimethoxy, R is methyl and R is t-butyl 34. A method according to claim 32 in which X is 3,4-dimethoxy, R is methyl and R is isopropyl. 

2. A method according to claim 1 in which X is lower alkyl, R is hydrogen, R1 is lower alkyl, R2 is hYdrogen, R3 is lower alkyl and n is
 1. 3. A method according to claim 2 in which X is 4-methyl, R1 is methyl and R3 is n-butyl.
 4. A method according to claim 2 in which X is 4-methyl, R1 is methyl and R3 is t-butyl.
 5. A method according to claim 2 in which X is 4-methyl, R1 is methyl and R3 is methyl.
 6. A method according to claim 2 in which X is 4-methyl, R1 is methyl and R3 is ethyl.
 7. A method according to claim 2 in which X is 4-methyl, R1 is methyl and R3 is isopropyl.
 8. A method according to claim 2 in which X is 2-methyl, R1 is methyl and R3 is isopropyl.
 9. A method according to claim 2 in which X is 2-methyl, R1 is methyl and R3 is t-butyl.
 10. A method according to claim 1 in which n is 0, R is hydrogen, R1 is lower alkyl, R2 is hydrogen and R3 is lower alkyl.
 11. A method according to claim 10 in which R1 is methyl and R3 is t-butyl.
 12. A method according to claim 10 in which R1 is methyl and R3 is t-butyl.
 13. A method according to claim 1 in which X is chlorine, R is hydrogen, R1 is lower alkyl, R2 is hydrogen, R3 is lower alkyl and n is
 1. 14. A method according to claim 13 in which the chlorine is in the 4-position, R1 is methyl and R3 is methyl.
 15. A method according to claim 13 in which the chlorine is in the 4-position, R1 is methyl and R3 is t-butyl.
 16. A method according to claim 13 in which the chlorine is in the 2-position, R1 is methyl and R3 is t-butyl.
 17. A method according to claim 13 in which the chlorine is in the 4-position, R1 is methyl and R3 is isopropyl.
 18. A method according to claim 13 in which the chlorine is in the 2-position, R1 is methyl and R3 is isopropyl.
 19. A method according to claim 13 in which the chlorine is in the 3-position, R1 is methyl and R3 is t-butyl.
 20. A method according to claim 13 in which the chlorine is in the 3-position, R1 is methyl and R3 is isopropyl.
 21. A method according to claim 13 in which the chlorine is in the 2-position, R1 is methyl and R3 is ethyl.
 22. A method according to claim 13 in which the chlorine is in the 2-position, R1 is methyl and R3 is methyl.
 23. A method according to claim 13 in which the chlorine is in the 2-position, R1 is methyl and R3 is n-propyl.
 24. A method according to claim 13 in which the chlorine is in the 2-position, R1 is methyl and R3 is n-butyl.
 25. A method according to claim 13 in which the chlorine is in the 2-position, R1 is n-butyl and R3 is isopropyl.
 26. A method according to claim 13 in which the chlorine is in the 2-position, R1 is n-butyl and R3 is t-butyl.
 27. A method according to claim 13 in which the chlorine is in the 2-position, R1 is n-butyl and R3 is methyl.
 28. A method according to claim 1 in which X is lower alkoxy, R is hydrogen, R1 is lower alkyl, R2 is hydrogen, R3 is lower alkyl and n is
 1. 29. A method according to claim 2 in which X is 4-methoxy, R1 is methyl and R3 is t-butyl.
 30. A method according to claim 28 in which X is 4-methoxy, R1 is methyl, and R3 is isopropyl.
 31. A method according to claim 28 in which X is 2-methoxy, R1 is methyl and R3 is t-butyl.
 32. A method according to claim 1 in which X is lower alkoxy, R is hydrogen, R1 is lower alkyl, R2 is hydrogen, R3 is lower alkyl and n is
 2. 33. A method according to claim 32 in which X is 3,4-dimethoxy, R1 is methyl and R3 is t-butyl
 34. A method according to claim 32 in which X is 3,4-dimethoxy, R1 is methyl and R3 is isopropyl. 